The only person who can clear Perry's client Robert Crane (Denver Pyle) of a murder charge is his sister Helen (Constance Ford), the wife of the murder victim. But Helen suffers from schizophrenia: by day, she is "herself" and by night she is her wild-and-reckless alter ego Joyce Martel. Unfortunately, it was "Joyce" who witnessed the murder, so Perry (Perry Mason) must figure out a way to put "Joyce", rather than Helen, on the witness stand! Though not based on an Erle Stanley Gardner original, this episode would seem to have been inspired by such multiple personality-themed films as Three Faces of Eve and Lizzie.
by Hal Erickson synopsis